(a) Field of the Invention
The present invention relates to a frequency synthesizer, a method of generating an output frequency thereof, and a method of correcting a conversion gain thereof.
(b) Description of the Related Art
A process of converting an analog signal to a digital signal is referred to as an analog to digital conversion. It is one of the most important performances of analog-digital conversion how accurately an analog signal can be converted to a digital signal.
A delta-sigma modulator (DSM) performs oversampling of an analog input signal and converts an oversampled input signal to a 1-bit digital bit or multi-bit digital data through delta-sigma modulation.
A frequency synthesizer using a DSM may have a deteriorated performance by quantization noise that is generated in the DSM.
A method of removing quantization noise includes a method of using a digital to analog converter (DAC). Thereby, a pattern of quantization noise that is generated in a DSM may be calculated using a DAC, and the calculated pattern may be compensated in an analog output that passes through a frequency divider, a phase detector, and a charge pump.
Here, a DAC is a circuit that converts a digital signal to an analog signal, and a conversion gain is changed according to whether a least significant bit (LSB) is set to which value. Because a removing degree of quantization noise is determined according to a conversion gain, a method of optimally making a conversion gain is necessary.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.